Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.
Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):14993-8. doi: 10.1073/pnas.1009321107. Epub 2010 Aug 9.
Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.
在四维超快电子显微镜的发展方面取得了进展，这使得对凝聚相结构动力学的时空成像成为可能。在超快电子显微镜中，电子被加速，通常加速到 200keV，并且显微镜以透射模式运行。在这里，我们报告了使用场发射源配置的扫描超快电子显微镜的发展。脉冲的扫描是在单电子模式下进行的，其中脉冲中最多包含一个或几个电子，从而实现了没有电子间空间电荷效应的成像，并且仍然在十（s）秒内完成。对于成像，检测来自表面结构的二次电子，这里演示了材料表面和生物标本的情况。通过记录背散射电子，还获得了来自单晶的衍射图案。具有所获得的时空分辨率的扫描脉冲电子显微镜及其高效的散热特性，现在有望提供原位 4D 成像和环境能力。
